The Filtration Behavior of Five Geotextiles Under Cyclic Flows
Date Issued
2011
Date
2011
Author(s)
Liu, Jia-Haur
Abstract
The use of geosynthetics for revetment protection is an environmentally friendly method. For example, the geotextiles lying on the revetment will interact with the soil to form a soil-geotextile filtration system. In a proper designed system, it must have the capabilities of good drainage and preventing the on-site soil from being washed away.
Most of the researches so far have conducted tests under uni-directional flow condition. In real condition, a flow goes into-and-out of a revetment due to water table change is more like bi-directional and cyclic than uni-directional. Hence, this research utilized a bi-directional flow apparatus and performed a series of tests on five non-woven geotextiles to test their filtration function. The soil, containing more than 20% of fines, was obtained from the bank of Tan-Han creek. The geotextiles for testing have different characteristic opening sizes and thicknesses. When tested, specimens of soil with geotextiles were under an overburden pressure of 70 kPa and various flow periods, ranging from 600 to 75 sec/cycle. During each test, the pore water pressure in the specimen and the settlement at the top of the specimen were measured. After each test, the soil washed away from the specimen was collected for analyzing its grain size distribution in order to understand if the filtration system was effective.
The test results are listed as follows: (1) from the analysis of grain size distribution and the weight of collected soil, it is known that all the geotextiles tested functioned well; (2) in the soil with high fines content, the variation of pore water pressure was not very stable due to the movement of fines. This phenomenon was obvious when the flow period was short; (3) under fast flows, the movement of fines induced rearrangement of soil structure and lead to apparent settlement; (4) the thicker geotextiles could reduce the disturbance from the flow than the thinner.
Subjects
geotextiles
filtration
characteristic opening size
bi-directional flow
revetment
Type
thesis
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